Pollution taxes and standards: A continuum of quasi-optimal solutions

A generalized second-best problem, involving a perfectly competitive industry which produces a pollution type of externality, is examined. The pollution tax is allowed to assume an arbitrary value (possibly zero), while a pollution standard, set as a ratio of pollution to output, is determined by a first-order optimizing condition. The general condition for a set of quasi-optimal solutions includes the Pareto-optimal solution as a special case. It is also found that when the pollution tax is below the optimal level, the usual implication is that the standard should be set so that the marginal cost of pollution reduction exceeds the marginal external damage.     

A MODELING APPROACH FOR OPTIMUM SEDIMENT DETENTION POND DESIGN1

ABSTRACT: A design procedure to determine optimum size for a sediment detention pond is presented. The procedure is based on simulating the sediment removal efficiency of the pond in conjunction with temporal variations in rainfall and potential land use and/or management options. The simulation procedure is based on a combined probabilistic-deterministic modeling approach. The probabilistic model generates daily rainfall with hourly increments for a selected site. The deterministic model simulates sediment yield and concentration for drainage area (pond inflow) and sediment trapping efficiency of the pond. The sediment yield and concentration in pond effluent is estimated from the difference between sediment inflow to the pond and sediment trapped by the pond. As an example, the procedure is applied to determine optimum design for a sediment detention pond in a surface mined area using several pond design options and alternative mining operation/land reclamation strategies.     

Interactive effects of CO2 and O3 on a ponderosa pine plant/litter/soil mesocosm.

To study individual and combined impacts of two important atmospheric trace gases, CO2 and O3, on C and N cycling in forest ecosystems; a multi-year experiment using a small-scale ponderosa pine (Pinus ponderosa Laws.) seedling/soil/litter system was initiated in April 1998. The experiment was conducted in outdoor, sun-lit chambers where aboveground and belowground ecological processes could be studied in detail. This paper describes the approach and methodology used, and presents preliminary data for the first two growing seasons. CO2 treatments were ambient and elevated (ambient + 280 ppm). O3 treatments were elevated (hourly averages to 159 ppb, cumulative exposure > 60 ppb O3, SUM 06 approximately 10.37 ppm h), and a low control level (nearly all hourly averages <40 ppb. SUM 06 approximately 0.07 ppm h). Significant (P < 0.05) individual and interactive effects occurred with elevated CO2 and elevated O3. Elevated CO2 increased needle-level net photosynthetic rates over both seasons. Following the first season, the highest photosynthetic rates were for trees which had previously received elevated O3 in addition to elevated CO2. Elevated CO2 increased seedling stem diameters, with the greatest increase at low O3. Elevated CO2 decreased current year needle % N in the summer. For 1-year-old needles measured in the fall there was a decrease in % N with elevated CO2 at low O3, but an increase in % N with elevated CO2 at elevated O3. Nitrogen fixation (measured by acetylene reduction) was low in ponderosa pine litter and there were no significant CO2 or O3 effects. Neither elevated CO2 nor elevated O3 affected standing root biomass or root length density. Elevated O3 decreased the % N in coarse-fine (1-2 mm diameter) but not in fine (< 1 mm diameter) roots. Both elevated CO2 and elevated O3 tended to increase the number of fungal colony forming units (CFUs) in the AC soil horizon, and elevated O3 tended to decrease bacterial CFUs in the C soil horizon. Thus, after two growing seasons we showed interactive effects of O3 and CO2 in combination, in addition to responses to CO2 or O3 alone for a ponderosa pine plant/litter/soil system.     

Dissipation and mobility of permethrin in the field with repeated applications under tropical conditions

Studies on persistence, mobility and the effect of repeated application of permethrin on its half-life were carried out under field conditions. The half-life of permethrin in the top 20 cm of the soil increased from 11.5 to 23.6 days as the application rates increased from 35 to 140 g ha(-1). Induced by heavier rainfall, more residues moved downward in trial 2 than in trial 1. Repeated applications enhanced degradation rates and mobility of permethrin in the soil. The residue level in the 0-5-cm layer was reduced at day 28 after 17 consecutive applications to a level lower than after 5 applications. The half-life of permethrin was reduced from 15.9 days to 11.2 days after 5 and 17 applications, respectively. The residue reached the 15-20 cm layer much earlier (approximately 3 days after treatment) in soil that received 17 applications as compared to those with two applications.     

Field investigation into unsaturated flow and transport in a fault: model analyses

Results of a fault test performed in the unsaturated zone of Yucca Mountain, Nevada, were analyzed using a three-dimensional numerical model. The fault was explicitly represented as a discrete feature and the surrounding rock was treated as a dual-continuum (fracture-matrix) system. Model calibration against seepage and water-travel-velocity data suggests that lithophysal cavities connected to fractures can considerably enhance the effective fracture porosity and therefore retard water flow in fractures. Comparisons between simulation results and tracer concentration data also indicate that matrix diffusion is an important mechanism for solute transport in unsaturated fractured rock. We found that an increased fault-matrix and fracture-matrix interface areas were needed to match the observed tracer data, which is consistent with previous studies. The study results suggest that the current site-scale model for the unsaturated zone of Yucca Mountain may underestimate radionuclide transport time within the unsaturated zone, because an increased fracture-matrix interface area and the increased effective fracture porosity arising from lithophysal cavities are not considered in the current site-scale model.     

Effects of nitrogen and phosphorus limitation on the activated sludge biomass in a kraft mill biotreatment system.

Unlike wastewater, pulp and paper mill effluents are generally severely deficient in bioavailable nitrogen and phosphorus. The influence of nitrogen and phosphorus limitations on steady-state or typical pulp and paper mill activated sludge floc properties and performance was studied using a bioreactor-fed synthetic raw mill effluent and seeded with mill activated sludge. Limitation of either nitrogen or phosphorus decreased growth, five-day biochemical oxygen demand, and suspended solids removal. Nitrogen limitation greatly enhanced activated sludge floc poly-beta3-hydroxybutyrate (PHB), but not carbohydrate or extracellular polymeric substances (EPS). In contrast, phosphorus limitation increased total floc carbohydrate and EPS, but not PHB. The flocs showed little ability to store either nitrogen or phosphorus. Nitrogen limitation, but not phosphorus limitation, produced much more negative net floc surface charge, increasing fines, while phosphorus limitation, but not nitrogen limitation, increased the floc bound water content and surface hydrophobicity and decreased fines.     

Environmental reporting for global higher education institutions using the World Wide Web

Voluntary environmental reporting on the progress achieved against policy objectives is an emerging trend in industry and business and is recognized as a valuable aid in implementing policy and improving environmental management systems. Environmental reporting in the UK, has a whole range of formats including PERI, GEMI, WICE and EMAS, with the last, in particular, aiming to improve the level of environmental stewardship and to increase the flow of environmental information to audiences both internally and externally. Higher education institutions globally have been slow to respond in this respect and there is much that they can learn from corporate environmental reporting. An environmental policy is not sufficient proof of commitment for those institutions who have signed the global Talloires Declaration or the European COPERNICUS Charter: demonstrable progress in policy implementation is essential. The environmental management systems that higher education institutions adopt or create and the ways in which their environmental information is collated are of great significance, but the medium selected for the report is perhaps one of the most important aspects to consider. Those institutions such as the University of Sunderland, UK who are using the World Wide Web have been able to produce a flexible, hypertext-linked service on request with inbuilt feedback mechanisms containing varied, up-to-date, comprehensive and well-structured environmental information signposted to external pro-active institutions and agencies. These reports have unique educational angles and reveal links and networks that are naturally more pervasive and far-reaching in their scope and impact and could well provide a key way forward to practical and sustainable environmental reporting into the millennium.     

Distribution,movement and diet of the snailSearlesia dira in the intertidal community of San Juan Island,Puget Sound,Washington

Searlesia dira Reeve is a locally abundant, carnivorous gastropod that occurs from Alaska to central California. I studied populations of this snail at a variety of sites on San Juan Island in order to provide information on their distribution and abundance and to analyze their community role, i.e., their potential impact on their prey populations and their dietary overlap with co-occurring invertebrate predators. I established permanent transects, both random and in crevices, at three areas of differing exposure to wave action. On these transects I recorded the number and size ofS. dira, activity, distance to nearest neighbor, other organisms present, and tidal height on four phases of the mixed semi-diurnal tidal cycle. The results are (1) an increase in density with increase in substrate relief, (2) an occurrence of highest densities in moderately exposed and exposed sites rather than in protected ones, (3) an increase in mean size with increase in depth along the intertidal gradient, (4) an increase in both total activity and feeding success on the high water immediately following an extreme minus low tide occurring during the daytime in the summer, (5) a relative restriction of feeding success to that high tide, and (6) a similarity of the diet to the relative abundance of the main observed prey for most areas. The main exceptions are chitons and one lower intertidal limpet, all of which are taken in excess of their apparent abundance and especially in the middle intertidal. The upward extension of some lower intertidal prey populations, such as chitons, may be limited by the increased susceptibility of individuals at the upper margin of the population to predators such asS. dira; susceptibility appears to be increased after periods with a higher probability of increased physiological stress, such as extreme low tides on summer days.